1. Field of the Invention.
This invention relates to devices for the stimulation of geothermal wells.
2. Description of the Prior Art.
Just as there are more dry holes drilled for oil, gas, and now for geothermal fluids than there are successful ones, so also there are more marginal and sub-marginal producers drilled than there are initially producers. Thus, the developer of a geothermal field, unless blessed with extreme luck, will quickly find himself faced with "almost" commercial wells. His problem is then how to increase the production of wells that have failed to produce in commercial quantities. Also, he is faced with the corollary problem of how to stimulate already commercial wells in order to achieve greater production from them to make up for losses accrued from the drilling of non-commercial wells.
Geothermal wells may be stimulated by means of explosives. More specifically, geothermal wells may be stimulated by means of shaped charges which blast pencil-shaped jets of liner material into rock strata crushing and penetrating the rock, cement and tubing and allowing geothermal fluids to seep through from the perforated materials into the main bore-hole of the well. However, when one wishes to utilize shaped charges to stimulate the production of geothermal wells one is faced with two problems -- temperature and fluids under pressure.
The temperature near the bottom of a geothermal well where one normally wishes to blast is ordinarily extremely high. When a shaped charge is lowered into this high temperature a problem of preventing what is commonly called "cook-off" of the explosive arises.
The pressure of geothermal fluids in the depths of a geothermal well is ordinarily high. Shaped charges generally utilize cone-shaped liners which collapse when the explosive is detonated and focus the pencil-shaped jets spoken of above. When such a cone is filled with high-pressure geothermal fluid, the fluid interfers with the proper collapse of the cone and the jet does not get properly formed.